In the past decades, lithium-ion batteries (LIBs) have been widely utilized in various applications such as consumer electronics because of their superior energy density, long life type and discharging capability. LIBs generally include an anode, an electrolyte, and a cathode that contains lithium in the form of a lithium-transition metal oxide.
In recent years, LIBs have been used in significant quantities for automotive propulsion because these batteries can provide many years of reliable service and are expected to last for about 10 years under normal driving conditions. LIBs may subsequently be used for utility energy storage and are eventually considered to have reached the end of their useful life.
Environmental issues of spent LIBs have attracted widespread concern in the public. If usable materials can be recovered from used batteries, less raw materials need to be extracted from the limited supplies in the ground. In addition, significant negative environmental impacts caused by mining and processing ores (e.g., SOx emissions from smelting of sulfide ores, such as those that yield copper, nickel, and cobalt) are avoided if the used LIBs can be recycled.
Currently, methods for recycling waste LIBs can be divided into two broad types: leaching method, and combination method of calcination and leaching. Generally, leaching method includes steps of crushing or chopping battery, leaching with acid, separating the leached materials by precipitation, complexation and/or extraction. However, leaching involves complex leachate composition and multiple separation steps creating large amounts of secondary waste.
Combination method of calcination and leaching includes steps of crushing or chopping battery, calcinating, leaching with acid, separating the leached materials, etc. However, this method has the additional disadvantage of high energy consumption caused by the heat treating process. Besides, recovery rate of the electrode materials is low since some components of the electrode materials are burned into carbon dioxide and other harmful substances.
Different attempts have been made to solve the problems and improve the performance of the recycling process. CN Patent Publication No. 104577246 A describes a method of recycling cathode and anode materials from LIBs. However, the method is time-consuming and labor-intensive since the recycling method requires removal of battery shell.
CN Patent Publication No. 103449395 A discloses a method for recycling a cathode material from lithium iron phosphate batteries. However, the method requires a step of meticulously disassembling lithium iron phosphate batteries to obtain undamaged cathode plates and is limited to lithium iron phosphate batteries.
CN Patent No. 101318712 B discloses a method for recovering cobalt from LIBs. However, the recycled content is only limited to LiCoO2, and not applicable to other cathode materials.
CN Patent Publication No. 104409792 A discloses a method for recovering cobalt from LIBs. The method comprises a step of separating materials of different densities based on a sink-float method where a heavier fraction sinks to the bottom, and a lighter fraction floats. This separation system although conceptually very simple suffers from a number of drawbacks. When the solid material is wetted with water or an aqueous liquor, some of the light and heavy particles flocculate to form aggregates. It is, therefore, a part of the suspended solid particles containing LiCoO2 and carbon powder will settle and be removed when separating the heavier fraction, thereby complicating the separation process. In addition, the method is time consuming and not economical since the lighter fraction, heavier fraction, and suspended solid particles must be removed sequentially. Furthermore, the recycled content is also limited to LiCoO2, and not applicable to other cathode materials.
In view of the above, there is always a need to develop a method for recycling LIBs with high recovery, high efficiency and low cost under mild conditions. In particular, a non-polluting method for recycling LIBs is needed to reduce air and water pollution formed in the recycling process.